Imaging of the hybridisation of nucleic acid probes including probes to nucleic acid targets including DNA targets is a key technology of modern biology, underpinning molecular, genomic and nucleic acid/DNA diagnostic methods.
Radiolabelling is one option, such as for membrane hybridisation, but it is difficult to extract quantitative results and to differentiate multiple labels. Fluorochrome methods offer advantages, especially with systems using optical lenses including microarrays, microscopes and flow cytometers. Various technologies have been used in biology for fluorescence wavelength detection, including dichoroic bandpass emission filters, emission-prism systems, grating methods and Raman spectroscopy. At least the first three have been applied to microarray readout systems.
Illustratively, reference is made to U.S. Pat. No. 5,784,162 which describes spectral bioimaging methods for biological research, medical diagnostics and therapy. The system consists of an exciting light source; a biological target (which might be a microarray) labelled with two or more fluorochromes; collecting optics; an interferometer; exit optics; and a two-dimensional array of detector systems. For a microarray experiment with two fluorochromes, with peak emissions at wavelengths L1 and L2 and characteristic excitation and emission spectra, the result of the experiment may be, for example, the difference in intensities;D=I(L1)−I(L2)
The spectrometer elements can be arranged so that the signal arriving at each pixel of the output detector is proportional to the density difference D emitted from a given point in the sample. The D intensity scale is then mapped onto a false colour scale for display, so that for example a point for which I(L1)>>I(L2) will appear red and so on. The system relies on using the interferometer to construct linear combinations of intensities emitted at specific wavelengths.
The present invention offers a new development in detection systems for biological assays.